Currently, short light pipes are used for fulfilling certain automotive exterior lighting functions by incorporating optics with light sources mounted at either one or both ends of the light pipe. Non-functional decorative light pipes are not commonly used in automotive applications. Alternatively, functional light pipes are optimized to produce a specific beam pattern to meet photometric requirements of functions such as parking lamp or tail Lamp, for example. The functional optimization typically overrides any consideration of uniform lit appearance of the light pipe.
However, the new trend in automotive lighting is to add non-functional light pipes for vehicle aesthetics. While ring-shaped light pipes inherently offer a uniform lit appearance, long straight or curved light pipe designs are very challenging to create the uniform lit appearance throughout an entire length of the light pipe, especially when a light source is mounted at only one end of the light pipe. In this case, the lit appearance of the light pipe is typically very bright in the region nearest the light source, and dimmer towards the other end. Such noticeably varying brightness along the length of the pipe at any viewing angle is preferably avoided to provide an acceptable appearance for the light pipe, since the sole aim of the light pipe is illumination styling and not an optical function.
It would be desirable to produce a light system including a light pipe wherein the light system provides a substantially uniform lit appearance along a length of the light pipe, while minimizing “hot spots” and noticeably varying brightness at light-coupling ends and curved portions of the light pipe.